Process for preventing the fulling shrinkage of wool



United States Patent 0 PROCESS FOR PREVENTING THE FULLING SHRINKAGE OF WOOL Charles R. Barnes, Pittsburgh, Pa., assignor to Albany {felt Company, Albany, N. Y., a corporation of New ork No Drawing. Application April 15, 1949, Serial No. 87,854

11 Claims. c1. 8-128) My invention relates to a method of treating wool and woolen fabrics to prevent the fulling shrinkage thereof. It is a well established fact that, when wool is allowed to react with chlorine, its felting properties are substantially destroyed, and, if the treatment is applied to a finished woolen fabric, the fabric will, thereafter, undergo little, if any, fulling or washing shrinkage. However, all of the heretofore proposed methods for treating wool with any of the halogens always result in damage to the wool fibers. In my process, the wool is caused to react with the nascent bromine under conditions which result in little or no damage to the wool as compared to the damage resulting from the oxidation encountered in other proposed halogenation processes.

According to my invention nascent bromine is evolved by effecting a reaction between appropriate materials, or otherwise, at such a rate and in such close proximity to the wool that the wool is caused to react therewith within a period as short as one second or less and while the bromine still remains in its nascent state. Nascent bromine derived and applied to wool in the proper manner has been found to eliminate fulling shrinkage entirely with substantially no wool damage.

Various halogenation process have been previously proposed for shrinkproofing wool. These may be summarized as follows:

(a) The treatment of wool with aqueous or non-aqueous solutions of chlorine, bromine or iodine.

(b) The treatment of wool with gaseous chlorine or bromine.

(c) The application of hypohalites either in the form of the hypohalous acids or by the action of acids on alkali or alkaline earth metal hypohalites.

(d) The chlorination of wool by the action of potassium permanganate on organic nitrogen chloro compounds or upon hypochlorites.

(e) Chlorination of wool by the action of the hydrolysis in water solution of compounds capable of yielding chlorine such as chromyl chloride, 1,3-diehloro 5, 5 dimethyl hydantoin, aktivin or chlorosulfonamids.

(f) Chlorination of wool by the controlled addition of acids to alkali hypochlorites containing protective agents such as organic amines.

These heretofore proposed processes depend upon the use of strong oxidizing agents which may damage wool considerably. For example, the process which employs the reaction of potassium permanganate upon organic nitrogen chloro compounds or hypochlorites, not only involves the use of the strongly oxidizing permanganate ion but also chlorine with a valence of plus one resulting as a product of the reaction. Furthermore, the permanganate process requires a final bleaching agent to remove the decomposition products of the permanganate.

My new and improved process for preventing the fulling shrinkage of wool with nascent bromine comprises saturating the wool or woolen fabric, which has been previously thoroughly wetted with water, with an alkali 2,714,051 Patented July 26, 1955 metal bromate and an alkali metal bromide in molar ratios of one to five, and then treating it with an acid to convert very gradually the bromate and bromide ions absorbed by the wool into bromic and hydrobromic acids, whereupon these acids react with each other rapidly to produce nascent bromine which, in turn, is reacted with the clean wool within a short period of about one second. Thus, substantially no free bromine or hypobromous acid harmful to the wool is evolved when the processing is properly controlled.

In order properly to carry out the treatment, the rates of the following two reactions must be carefully controlled, namely:

(1) The rate of production of nascent bromine; and

(2) The rate of reaction of the nascent bromine with the wool.

The rate at which the nascent bromine is produced is controlled by the rate at which the alkali metal bromate and bromide salts of the solution absorbed by the wool are converted into bromic and hydrobromic acids, respectively. The factors which effect the conversions are: (a) the amount of available hydrogen ion present; (b) the concentration of the solution; (a) the temperature of the solution; and (t!) the presence of those salts in the solution which catalyze the reaction.

The rate at which the nascent bromine reacts with the wool is governed by-(a) the cleanliness of the wool; and (b) the temperature. Therefore, by controlling not only those factors which affect the production of the nascent bromine but also those which afi'ect its reaction with the wool, it is possible to cause the wool to react with the nascent bromine as rapidly as it is produced in immediate contact with the wool.

Regarding those factors which affect the rate of conversion of the alkali metal bromate and bromide to bromic and hydrobromic acids, respectively, the first, as pointed out above, is the availability of hydrogen ion. This is controlled by the very gradual addition of an acid, preferably a mineral acid, in order to satisfy the following typical equations in which potassium bromate, potassium bromide and sulfuric acid are employed:

Another important factor affecting the rate of conversion is the presence of such salts in the solution which catalyze the above halogen-acid producing reactions. By selection of the alkali metal bromates and bromides and the acids, it is possible to produce automatically those salts as lay-products which are catalysts for the conversion reactions. For example, potassium bromate and bromide may be used in conjunction with sulfuric acid to produce potassium sulfate as a by-product which acts as an automatic catalyst for the conversion reaction, or, in the same manner and for the same purpose, the bromate and bromide salts of sodium may be used in conjunction with hydrochloric acid to produce automatically the catalyst sodium chloride.

The formation of bromic and hydrobromic acids may also be catalysed by using excess mineral acid. However, this procedure is limited since too much acidity causes wool damage. It is preferred to brominate the wool in the present process within the pH range of 1.5 to 6.0, and a pH value as low as 1.0 may be used.

The formation of bromic and hydrobrornic acids is also controlled by their concentrations in solution; high concentrations tend to speed up their formation while low concentrations retard it. Therefore, it is preferred to use as small a liquor to goods ratio as possible. It is seldom necessary to have this ratio greater than 6 /2 to 1 and, depending upon the method of impregnation and '1 i: the apparatus used, the ratio may be decreased even further.

Another factor which affects the rate of conversion into acids of the alkali metal bromates and bromides is the temperature of their solutions. Low temperatures retard while high temperatures enhance the formation of the acids which subsequently react with each other to produce nascent bromine. In actual practice the temperature may range from 32 to 125 F., or even 150 F., but I prefer to employ a temperature near 80 F., which promotes the production of nascent bromine at the optimum rate. If the nascent bromine is produced at a greater rate than the wool can react with it, free molecular bromine will form, accumulate in the solution, and cause wool damage. Both bromic acid and hydrobromic acid are colorless, but bromine is dark colored. Hence, the formation in the treating solution of free molecular bromine in substantial quantities will be apparent by the brownish discoloration of the solution caused thereby.

Regarding the rate at which wool can react with nascent bromine from the solution with which it is saturated, one factor in addition to temperature is important, namely, the cleanliness of the wool. The presence of any residual grease. soap. etc.. tends to retard the bromiuation. Therefore it is desirable to clean the wool before treatment to at least a grease content of 0.5% and preferably to 0.2%.

My process may be carried out on woven woolen fabrics as follows:

The fabric. thoroughly washed and rinsed free of grease and soap. is saturated in the wetted out state with a solution containing stoichiometrical amounts of an alkali metal bromate and an alkali metal bromide. When a dyetub is used for the impregnation, the liquor to cloth weight ratio preferred. at this stage of the process, is /1 to l. The quantities of alkali metal bromate and bromide salts required in the liquor are determined by the degree of shrinkproofing desired, and the shrinking effects of various percentages of available nascent bromine in the bromute and bromide salts present in stoichiometrical proportions in the liquor are shown in Table I below.

A solution containing a stoichiometrical quantity plus 200% excess of acid with reference to the quantity of the bromate and bromide salts is now added gradually over a fifteen minute period to the liquor in the dyetub while the machine is running with the fabric. The temnerature of the liquor during bromination is preferably maintained near 80 to 85 F. The final ratio of the weight of the liquor to that of the goods after all the acid if is added is preferably 6 /2. to 1 when the dyetub method is employed. Larger ratios may be used satisfactorily but the time required for the production of the nascent bromine in the liquor is increased. Under the above conditions the wool exhausts the liquor completely of its nascent bromine content in a period of from 30 to 50 minutes.

After the bromination is complete the woolen fabric is rinsed lightly with water and treated with 1% of sodium hisulfite based on the weight of the fabric in order to remove any unreacted brornate or any loosely bound bromine compounds from the wool.

Finally. the fabric is neutralized by a treatment with 4% of sodium bicarbonate based on the weight of the wool. rinsed free of salts. and dried without tension; care being taken to avoid setting up in the fabric any artificial lfil'l-ilQIlS which may result in relaxation shrinkage.

While I prefer to use sodium bromate and bromide with hydrochloric acid. or the corresponding potassium salts with sulfuric acid. other acids such as phosphoric, nitric, acetic, hydroxyacetic. etc, may be used for the conver sion of the alkali metal bromate and bromide to bromic and hydrobromic acids, respectively, but sulfuric or hydrochloric acids are preferred because of their relatively low costs. In the process, metal bromates and bromides other than sodium and potassium may be employed. In fact any metal brornate and bromide capable of yielding in water solution bromic and hydrobromic acids, respectively, are satisfactory for the production of nascent bromine as a shrinkproofing agent for wool.

Various methods of exercising the invention may be followed. The wool may be impregnated with a mixture of the bromate and bromide and the acid added later; or it may be impregnated with a bromide, and the acid and bromate thereafter brought in contact with the wool; or any other method which brings the three ingredients into reaction in the presence of wool may be employed. My process may be conducted either as a batch process in the dyetub, or as a continuous process where the fabric is padded with the bromate, bromide and acid either separately or in combinations and in the proper proportions so that the nascent bromine produced reacts with the wool as rapidly as it is formed.

The process may be applied to the wool before carding, to the yarn after spinning, or to Woven or knitted fabrics either before or after dyeing. and therefore the term wool," as used herein, is to be understood as including not only wool fibers but also yarns, fabrics, etc., formed in whole or in part from such fibers. The time of its applications will depend in part upon the method of finishing to be applied to the goods. if, for example, the fabric is to be fulled, the treatment cannot be applied until fulling is finished.

In order that the application of my invention to woolen cloth may be more thoroughly understood, I cite the following example. There are, of course. many other forms in which the invention may be used to shrinkproof wool because, in its broader aspects. the basic feature thereof is the production of nascent bromine and, substantially simultaneously therewith, effecting a reaction thereof with the wool to be treated.

Example A piece of 10 ounce grey flannel 54 inches wide with a total weight of 34 pounds and containing 70% wool and 30% cotton was sewn together at the ends and charged into a small industrial dyetub. 163 pounds of water were added to the tub and the machine started. After the cloth was thoroughly wetted up, pounds of a solution containing 0.37 pound of sodium bromate and 1.3 pounds of sodium bromide were added to the bath. After thorough mixing and with the machine still running, 4.5 pounds of hydrochloric were mixed with 34 pounds of water and the resulting solution was added very gradually to the bath over a 15 minute period. After the acid addition the machine was kept running for 30 minutes more with the bath at a temperature of 83 F.

The solution was dropped and a light rinse followed.

A second bath was now applied for 10 minutes which contained 0.68 pound of sodium bisulfite in gallons of Water.

The second bath was dropped and a short rinse followed.

A third bath containing 1.3 pounds of sodium carbonate in 50 gallons of water was now applied for 10 minutes, after which the bath was dropped and a 20 minute rinse followed.

A comparison of shrinkage during washing, of tensile strength and of alkali solubility between the untreated starting material and the treated material under equal conditions is as follows:

The shrinkproofing effect of reacting various amounts of nascent bromine with the wool is shown in Table I below where various percentages of nascent bromine were applied by my process to white flannel containing 70% wool and 30% cotton. The percentages of nascent bromine were varied from 0.01% to 10% based on the weight of the cloth. The shrinkages were measured after washing for eight hours in an "Easy Whirldry Washer with 0.5% laundry soap solution maintained at 120 F., by an automatic thermostat; the tensile strengths were determined by tests on strips having the same number of warp ends; and the alkali solubilities were determined by the procedure described by Harris, M., and Smith, A. L., Journal of Research, National Bureau of Standards, vol. 17, pages 577583 (1936).

TABLE I Effect of concentration of nascent bromine on falling shrinkage and other properties of the fabric l Concentration of I g a Nascent Shflnka u Tensile Alkali Trial No. Bromine arm g Strength, Solubility,

as Percent l l lbs. Percent based on as 1mg cloth 8 hours 0. 01 9. 1 l3. 8 0.05 10.1 41.2 in, 0.10 11.3 41.3 14.3 1. 12. 1 40. 8 l5. 5 3.50 0.4 41.0 14.3 5. 00 0. 6 40. 9 27.0 6.00 -l. l 40. 0 3i. 2 7. 00 0. 0 42. 0 33. 7 10. 00 0. l 39. l 40. 9

Control 0. 00 18. 2 42. 6 13.3

What I claim is:

l. The method of preventing the fulling shrinkage of wool by treating it in a water solution of three substances comprising an acid, and a metal brornate and a metal bromide capable of yielding in said water solution bromic and hydrobromic acid, respectively, when combined with said acid; said method comprising, first immersing the wool in a water solution of any two of said substances, and thereafter forming nascent bromine in said solution by adding said third substance thereto at a comparatively slow rate and less than that which will effect a substantial brownish discoloration of said solution; whereby to effect the formation of said nascent bromine in said solution at a rate approximating the rate it reacts with the wool and to prevent the formation of free molecular bromine in said solution; said bromate and said bromide being used in stoichiometrical amounts producing nascent bromine in a total quantity constituting from about 1% to about 5%, by weight, of the wool.

2. Those steps in the method of preventing the fulling shrinkage of wool which comprise immersing the wool in an aqueous bath, progressively forming nascent bromine in said bath, and preventing the formation therein of appreciable quantities of bromine in free molecular form by controlling and restricting the rate at which said nascent bromine is formed in said bath to less than that which will effect a substantial brownish discoloration of said bath; whereby to effect a reaction of said nascent bromine with said wool substantially concurrently with the formation thereof.

3. The method set forth in claim 2 in which the quantity of nascent bromine formed in said bath is from about 1% to about 5%, by weight, of the wool.

4. The method set forth in claim 2 in which the pH of the bath is maintained from 1.0 to 6.0.

5. The method set forth in claim 2 in which the pH of the bath is maintained from 1.0 to 6.0 and the temperature thereof is maintained from 32 R, to F.

6. The method of preventing the fulling shrinkage of wool which comprises saturating the wool with an aqueous solution containing an alkali metal bromate and an alkali metal bromide in the proportion of one mole of bromate to five moles of bromide and thereafter adjusting and substantially maintaining the pH of the solution from 6.0 to 1.0 by adding acid thereto at a rate less than that which will effect a substantial brownish discoloration of said solution.

7. The method of preventing the fulling shrinkage of wool which comprises treating the wool in an aqueous bath containing an alkali metal bromate and an alkali metal bromide in the proportion of one mole of bromate to five moles of bromide, and thereafter adding an acid to said bath at a comparatively slow rate and less than that which will effect a substantial brownish discoloration of said bath; whereby to prevent the formation of substantial quantities of free molecular bromine in said bath; the total quantity of bromate and bromide in said bath being such as to yield, upon reaction with said acid, a quantity of nascent bromine constituting from about 1% to about 5%, by weight, of said wool.

8. The method of preventing the fulling shrinkage of wool which comprises saturating the wool with an aqueous solution containing potassium bromate and potassium bromide in the proportion of one mole of the bromate to five moles of. the bromide, and thereafter adding sulfuric acid to said solution at a comparatively slow rate to effect, during said treatment, the progressive formation in said solution of bromic acid and hydrobromic acid, and potassium sulfate for catalyzing the reaction of said acids to form nascent bromine; the rate of addition of said sulfuric acid being less than that which will effect a substantial brownish discoloration of said solution, whereby to prevent the formation of substantial quantities of free molecular bromine or hypobromous acid in said solution.

9. The method of preventing the fulling shrinkage of wool which comprises saturating the wool with an aqueous solution containing sodium bromate and sodium bromide in the proportion of one mole of the bromate to five moles of the bromide, and thereafter adding hydrochloric acid to said solution at a comparatively slow rate to effect, during said treatment, the progressive formation in said solution of bromic and hydrobromic acid, and sodium chloride for catalyzing the reaction of said acids to form nascent bromine; the rate of addition of said hydrochloric acid being less than that which will effect a substantial brownish discoloration of said solution, whereby to prevent the formation of substantial quantities of free molecular bromine or hypobromous acid in said solution.

10. The method of p'rcventing the fulling shrinkage of wool which comprises immersing the wool in an aqueous bath, and thereafter simultaneously forming bromic acid and hydrobromic acid in said bath but at a comparatively slow rate and less than that which will effect a substantial brownish discoloration of said bath; whereby to effect the production of nascent bromine in said bath by the reaction of said acids, and a reaction of said nascent bromine with said wool without the formation of free molecular bromine in appreciable quantity in said bath.

11. The method of preventing the fulling shrinkage of wool by treating it in a Water solution of three substances comprising an acid, and a metal bromate and a metal bromide capable of yielding in said water solution bromic and hydrobromic acid, respectively, when combined with said acid; said method comprising, first immersing the wool in a Water solution of any one of said substances, and thereafter forming nascent bromine in said solution by adding said other two substances thereto at a comparatively slow rate and less than that which will effect a substantial brownish discoloration; whereby to effect the formation of said nascent bromine in said solution at 7 a rate approximating the rate it reacts with the Wool and 2,326,021 to prevent the formation of an appreciable quantity of 2,508,007 free molecular bromine in said solution.

References Cited in the file of this patent 1 .154 UNITED STATES PATENTS fig; 1,840,034 Hansen Jan. 5, 1932 2,158,446 Werft May 16, 1939 8 Ericsson Aug. 3, 1943 Bloch May 16, l950 FOREIGN PATENTS Great Britain 1906 Switzerland Feb. 17, 1930 Great Britain 1875 

1. THE METHOD OF PREVENTING THE FULLING SHRINKAGE OF WOOL BY TREATING IT IN A WATER SOLUTION OF THREE SUBSTANCES COMPRISING AN ACID, AND A METAL BROMATE AND A METAL BROMIDE CAPABLE OF YIELDING IN SAID WATER SOLUTION BROMIC AND HYDROBROMIC ACID, RESPECTIVELY WHEN COMBINED WITH SAID ACID; SAID METHOD COMPRISING, A FIRST IMMERSING THE WOOL IN A WATER SOLUTION OF ANY TWO OF SAID SUBSTANCES, AND THEREAFTER FORMING NASCENT BROMINE IN SAID SOLUTION BY ADDING SAID THIRD SUBSTANCE THERETO AT A COMPARATIVELY SLOW RATE AND LESS THAN THAT WHICH WILL EFFECT A SUBSTANTIAL BROWNISH DISCOLORATION OF SAID SOLUTION; WHEREBY TO EFFECT THE FORMATION OF SAID NESCENT BROMINE IN SAID SOLUTION AT A RATE APPROXIMATING THE RATE IT REACTS WITH THE WOOL AND TO PREVENT THE FORMATION OF FREE MOLECULAR BROMINE IN SAID SOLUTION; SAID BROMATE AND SAID BROMIDE BEING USED IN STICHIOMETRICAL AMOUNTS PRODUCING NASCENT BROMINE N A TOTAL QUANTITY CONSITUTING FROM ABOUT 1% TO ABOUT 5%, BY WEIGHT OF THE WOOL. 